where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

Hi-Spec Systems
Hi-Spec Systems are an innovative, forward thinking and fast moving non-destructive testing (NDT) technology company who specialise in the design ...

567 views
Technical Discussions
Patrick Huttenhuis
Patrick Huttenhuis
09:19 Jan-09-2003
NDT's for middle voltage cables

A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:

- a black (carbon) PE layer of appr. 0.5 mm
- a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
a black (carbon) PE layer of appr. 0.5 mm

After the extrusion the cable is vulcanised and cooled.

Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.

Thank you in advance for your advice.

Kind Regards,

Patrick Huttenhuis
Procede Twente B.V.
patrick.huttenhuis@procede.nl


    
 
 
Godfrey Hands
Consultant,
PRI Nadcap, United Kingdom, Joined Nov 1998, 295

Godfrey Hands

Consultant,
PRI Nadcap,
United Kingdom,
Joined Nov 1998
295
09:45 Jan-09-2003
Re: NDT's for middle voltage cables
: A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
: The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:
:
: - a black (carbon) PE layer of appr. 0.5 mm
: - a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
: a black (carbon) PE layer of appr. 0.5 mm
:
: After the extrusion the cable is vulcanised and cooled.
:
: Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.
:
: Thank you in advance for your advice.
.
: Kind Regards,
.
: Patrick Huttenhuis
: Procede Twente B.V.
: patrick.huttenhuis@procede.nl
.

Dear Partick,
Sounds as if an Electronics solution rather than an NDT solution may be able to detect these bubbles.
I suggest that you speak with some electronics experts.
My thoughts are that the bubbles inside the 5 mm layer will affect the effective dielectric constant, and looking at the electrical capacity between the aluminium pipe and a separate electrode on the outside of the wrapped cable may provide a solution.
The thicknesses however may be fairly high to have a measurable effect.

Veel succes met de toepassing.
I wish you success with the application.

Godfrey Hands


    
 
 
Jörg Collrep
Jörg Collrep
00:02 Jan-09-2003
Re: NDT's for middle voltage cables
Dear Patrick,
this kind of defects could easily be detected by shearography but not within the production speed as we need some time ( 3 - 5 sec )to excite the cable with a very low thermal or vacuum excitation and acquire an image under loaded and unloaded condition. If you would like to know more about the technique pls reply to me directly.
Thanks
Jörg Collrep
Steinbichler Optotechnik GmbH
www.steinbichler.de


: A client of us, a producer of middle voltage cables (up to 50 kV) has problems during the extrusion process. During the extrusion process once in a while there arise small bubbles (1-3 mm) in the isolating poly-ethylene layer. It is believed that this bubbles will result in undesirable voltage breakdown.
: The cable consists of a 12-22 mm aluminium pipe. Around this pipe a three layer polymer is constructed during one extrusion step. The three layers are:
:
: - a black (carbon) PE layer of appr. 0.5 mm
: - a white PE layer of appr. 5 mm. In this layer the bubbles have been seen,
: a black (carbon) PE layer of appr. 0.5 mm
:
: After the extrusion the cable is vulcanised and cooled.
:
: Do you know if there are non-destructieve methods (preferable online) which can indicate the bubbles in the polymer layer. If yes, what kind of methods are available, what are the conditions and advantage / disadvantages of the methods. The production speed of the cable is betwen 8 and 30 m/min.
:
: Thank you in advance for your advice.
.
: Kind Regards,
.
: Patrick Huttenhuis
: Procede Twente B.V.
: patrick.huttenhuis@procede.nl
.



    
 
 

Product Spotlight

Sci Aps Z-Series Portable Handheld Analysers

The world’s only handheld analyzer that measures carbon content in stainless (yes even L-grades),s
...
teels, and cast irons. Also accepted for low Si analysis for sulfidic corrosion analysis, and is widely used in the power industry for Cr analysis, for flow accelerated corrosion applications.
>

NDT Master Lecturer

In the program both university professors and practitioners will give lectures, which guarantees the
...
oretical depth and practical inside. Academic Director: Prof. Dr. Christian Boller
The following lecturers are not complete: Prof. Tadeusz Stepinski, Prof. Wieslaw Staszewski, Prof. Frank Walther, Prof. Giovanni Bruno, Prof. Gerd Dobmann, Prof. Philippe Guy
>

HARDNESS TESTER TKM-459CE combi

TKM-459CE combi applies 2 methods of hardness control: UCI and Leeb. It provides high-accuracy tes
...
ting of metals and alloys as well as items of different sizes and configurations, their hardened layers and galvanic coatings. Device represents results in HB, HRC, HV and others. Shock-, dust- and water-proof housing with intuitive software make this gauge easy to use in all working conditions.
>

ISONIC 3510

Very Powerful Superior Performance Extremely Portable Smart Phased Array Ultrasonic Flaw Detector an
...
d Recorder with 2 Conventional UT and TOFD Channels uniquely combines PA, single- and multi-channel conventional UT, and TOFD modalities providing 100% raw data recording and imaging. Suitable for all kinds of every-day ultrasonic inspections
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window